Valve adjustment intervals

[cookie]

Genuine question on this subject

I allways drain the oil when the bike is warm so it runs out nicely but doesnt the engine need to be stone cold to check/adjust valve clearances ???

yes.

drain warm oil, then refill and wait for the cold oil to cool the engine before doing the valves. this may still take some time.

Myke Rocks - for the past few years, cars have had self adjusting, hydraulic tappets. that's why they are never adjusted. i wouldn't buy a bike from you either.

 

[The Grey One]

yes.

drain warm oil, then refill and wait for the cold oil to cool the engine before doing the valves. this may still take some time.

Myke Rocks - for the past few years, cars have had self adjusting, hydraulic tappets. that's why they are never adjusted. i wouldn't buy a bike from you either.

Drain oil when it's hot not just warm. Just filling up with oil won't cool it down enough unless you wait for hours. Better to drain the oil one evening and adjust clearances next morning. We always did this with air cooled Citroen engines both twins and flat fours and it is what I do with my own GS. You need the right conditions for both operations, as they say, if a job is worth doing. Draining the oil without getting the engine hot could leave sludge & crap in the oil ways and adjusting the clearances when the engine is still warm will not give correct measurements so is as waste of time.

Some cars do have hydraulic tappets but not all. And remember that items have been cut from service schedules over the years, more to make the cars appear less expensive to maintain than any other consideration. A prime example of this is not checking brake wear, most manufacturers deleted this years ago and rely on the dashboard warning light telling drivers their brakes are worn out. A touching faith in warning lights!

John

 

[cookie]

a bit pedantic maybe?

 

[Welshman]

Genuine question on this subject

I allways drain the oil when the bike is warm so it runs out nicely but doesnt the engine need to be stone cold to check/adjust valve clearances ???

I only do it stone cold and it runs very nicely...

 

[MattW]

What the Greyone sez.

I do the oil change one day and the clearances the next morning / when I get round to it when it's cold.

I won't mention that I do all the fluids every 3000 (oil filter and clearances every 6k). What a waste of time, I suppose I should wait till the oil turns to treacle and it rattles like a tractor before looking at it

 

[The Grey One]

a bit pedantic maybe? [/QUOTE

If pedantic means not wanting to waste my time by not doing a job properly then guilty as charged.

John

 

[cookie]

If pedantic means not wanting to waste my time by not doing a job properly then guilty as charged.

John

it doesn't.

 

[seahorse]

I did my own service for the first time on my 1200 at 24k. Adjusted valves and end float so they were absolutely spot on. Checked since then at 30, 36, 42 and 48k, still exactly the same. Still check though, as already said its no great hardship when doing a service.
My Mondeo by the way doesn't even have valve clearance check till 100k!

 

[ianboydsnr]

Any clearance is the correct clearance when the engine is hot, the cold clearance takes into account of the thermal expansion, so if an engine is hot, then the fact there is some clearance albeit a minimum amount is the correct clearance!

Most yamaha's are done at 24k!

 

[monkeyboy]

So if they start to close up around 6,500 they will continue closing until you check them




Monkeyboy Sorry to disagree but the change is so gradual for most "riders" they wont know until it burns a bit out ad it gets really lumpy

OK, I understand that. I'm just going on personal experience. When I'm away for a long time I've taught myself not to obsess or worry about every tiny thing that could go wrong and if something is not broken then I will definitely not fix it - I'm genuinely interested in this though.

If a valve needs adjusting significantly because it's burning out - will adjusting it stop it burning out? I would have thought the burning was down to something else and all you're doing is delaying the inevitable? To me, this is a bit chicken and egg. Is bad valve adjustment causing the burn, in which case someone f'ked up the adjustment in the first place, or is something else causing the burn and so adjusting is just masking and compensating for another problem? My own experience tells me that valve seat wear is minimal over very high mileages and adjustment has been unnecessary. Everyone has said how they check their gaps regularly but nobody has said whether they need adjusting or not.

Yes - adjustment being necessary indicates a wearing valve and could be a warning sign of impending boom but IMO, just adjusting it may just be delaying it rather than curing it?

Still - its good that we're all different. It's certainly better to learn from other's mistakes rather than your own too.

 

[MattW]

OK, I understand that. I'm just going on personal experience. When I'm away for a long time I've taught myself not to obsess or worry about every tiny thing that could go wrong and if something is not broken then I will definitely not fix it - I'm genuinely interested in this though.

If a valve needs adjusting significantly because it's burning out - will adjusting it stop it burning out? I would have thought the burning was down to something else and all you're doing is delaying the inevitable? To me, this is a bit chicken and egg. Is bad valve adjustment causing the burn, in which case someone f'ked up the adjustment in the first place, or is something else causing the burn and so adjusting is just masking and compensating for another problem? My own experience tells me that valve seat wear is minimal over very high mileages and adjustment has been unnecessary. Everyone has said how they check their gaps regularly but nobody has said whether they need adjusting or not.

Yes - adjustment being necessary indicates a wearing valve and could be a warning sign of impending boom but IMO, just adjusting it may just be delaying it rather than curing it?

Still - its good that we're all different. It's certainly better to learn from other's mistakes rather than your own too.

There can be other reasons but the biggest cause of valves burning is lack of tappet clearance which stops the valve seating fully. This causes a minute (at first) leak of combustion gases which starts to erode the valve and seat in just one place. Once this erosion has started, it rapidly escalates until it's burned a big chunk out of the valve and knackered the seat. I'm sure Steptoe has posted pictures of burned valves before.

The actual process of it burning out won't affect the valve clearances (well, not until it gets really bad) - it doesn't work that way round - but over tight clearances will make it burn (eventually). So to answer your question above - yes - bad (over tight) adjustment causes the burn.

There are all sorts of reasons that valve clearances can tighten up (seat material problems, modern fuels, overheating, high mileages or just wear and tear) but sometimes there's nothing obvious and it doesn't always happen. As Steptoe says above, one bike can suffer and an identical bike won't and one bike might be ok for years and then have a problem - there's no way of telling.

Valve clearances are just one of the routine maintenance checks that are specified for this reason. You don't wait to check your oil until the bike starts making bearing noises - you do it as part of your routine maintenance / checks. It might seem pointless if every time you check, its always ok but that's what routine maintenance is all about - you're not fixing problems, you're preventing them...

 

[cookie]

OK, I understand that. I'm just going on personal experience. When I'm away for a long time I've taught myself not to obsess or worry about every tiny thing that could go wrong and if something is not broken then I will definitely not fix it - I'm genuinely interested in this though.

If a valve needs adjusting significantly because it's burning out - will adjusting it stop it burning out? I would have thought the burning was down to something else and all you're doing is delaying the inevitable? To me, this is a bit chicken and egg. Is bad valve adjustment causing the burn, in which case someone f'ked up the adjustment in the first place, or is something else causing the burn and so adjusting is just masking and compensating for another problem? My own experience tells me that valve seat wear is minimal over very high mileages and adjustment has been unnecessary. Everyone has said how they check their gaps regularly but nobody has said whether they need adjusting or not.

Yes - adjustment being necessary indicates a wearing valve and could be a warning sign of impending boom but IMO, just adjusting it may just be delaying it rather than curing it?

Still - its good that we're all different. It's certainly better to learn from other's mistakes rather than your own too.

the gaps tend to close in normal use before the valve starts "burning out". it's the gap closing to the point where the valve is being held slightly open that will rapidly accelerate the demise of the valve and burn it out.

the action of the valve spring slamming the valve shut can elongate the valve stem causing the gap to close, as can the action of the valve beating it's way into the head. these should be only very small changes in normal use, but it's common sense to monitor the the situation, hence the manufacturers specify a service schedule.

 

[DrFarkoff]

OK, I understand that. I'm just going on personal experience. When I'm away for a long time I've taught myself not to obsess or worry about every tiny thing that could go wrong and if something is not broken then I will definitely not fix it - I'm genuinely interested in this though.

Yup sensible A simple rider check everday to a bike you are living with should indicate anything out of the ordinary

If a valve needs adjusting significantly because it's burning out - will adjusting it stop it burning out?

I think(but have no evidence other than just experience) its a case of a badly adjusted valve will firstly not transfer heat to the seat and head whilst closed and run significantly hotter than a normally adjusted valve in the same conditions

If it's not seating correctly because it has no clearance then if you have even a whisper of incredibly hot combustion gasses roaring past at X thousand times a minute / Hour / Day its not long in starting an oxy acteylene type effect and making the hole bigger

Ever notice its "usually" exhaust valves that the heads fall off??

Yes - adjustment being necessary indicates a wearing valve and could be a warning sign of impending boom but IMO, just adjusting it may just be delaying it rather than curing it?

By servicing @ approximately the intervals and noting if valves were tight or unchanged between the services will give you an indication of its okay to go on a thousand miles or more

By my experience bikes that are thrashed up and down gears and held at 80 ~ 90 (plus) on motorways tend to close up and need adjusted every service

Bikes that are ridden with mechanical sympathy and occasionally ridden in a spirited (but not thrashed) may need one or 2 out of 8 adjusted,

People who pootle around are usually fine service to service

Maybe thats a generalisation but its what I have noticed

 

[snelly]

An engine that is too quiet is scary, there,s nothing wrong with a bit of valve rustle.If you don,t know what you are listening for, let someone who does know point you in the right direction. A bit too loose is always better than too tight.

 

[JJH]

If a valve/seat has started to burn out no amount of adjustment will cure it. People who have compared different bike and car valve adjustment are not comparing like with like. JJH

 

[DrFarkoff]

Yeah but "Why" is the main question? Valves shouldn't just "burn out"

There has to be an initialisation and in my instance the 1200 that dropped one on me was just on service interval.

I had just taken it about a mile up the road to warm up the oil for draining and as I turned in the T junction to head back the temp gauge was up to 3 or 4 bars and bam the head dropped off the exhaust valve and broke the other off.
I was just changing from 1st to second on a leaf covered road so over revving couldn't have been an issue I hadn't had it above 3500 rpm because it was like riding on snow

Interestingly enough the last people to touch it were the dealers! There wasn't much point checking the clearances afterwards as there were no heads to stop the valves

I often wonder, Did they even bother slipping back the rocker covers?? As while I was there there was constant pressure for time, and to get the job out!

Something starts the process End of story

If a valve/seat has started to burn out no amount of adjustment will cure it. People who have compared different bike and car valve adjustment are not comparing like with like. JJH

 

[MarkShelley]

By my experience bikes that are thrashed up and down gears and held at 80 ~ 90 (plus) on motorways tend to close up and need adjusted every service

Although I hardly ever go above 6K when accelerating, I always cruise circa 85mph. I would say over half of my miles are high speed motorway rides yet the valves have hardly ever need adjusting in the six or so times I have checked them, and when they did need it the adjustment was miniscule. I reckon they probably vary a little bike to bike, just like oil useage seems to.

 

[DrFarkoff]

I'd class you in this group then

Bikes that are ridden with mechanical sympathy and occasionally ridden in a spirited (but not thrashed) may need one or 2 out of 8 adjusted,

Although I hardly ever go above 6K when accelerating, I always cruise circa 85mph. I would say over half of my miles are high speed motorway rides yet the valves have hardly ever need adjusting in the six or so times I have checked them, and when they did need it the adjustment was miniscule. I reckon they probably vary a little bike to bike, just like oil useage seems to.

 

[duckspeed]

Think it depends on the quality of fuel used..
Said he poking hornets nest with long stick....



Sent using witchcraft

 

[snelly]

The valve stems and the heads are usually made of different grade material because of the different thermal properties and jobs the valve heads and stems do. The join will be the weak point.Nothing mechanical is ever perfect. But we can help with good maintenance practices.